The great American humorist Will Rogers famously quipped, "I am not a member of any organized political party. I am a Democrat" (see here). The Republicans traditionally have been viewed as a more cohesive party, if not exactly marching in lock-step, at least holding to certain core principles and goals.
The current impasse over the government shut-down and the looming debt-ceiling debacle demonstrates more than any previous political issue that the Republicans have become at least as disorganized as Rogers' old Democrats. The GOP is fractured by disagreements not between moderates and conservatives, who are generally united on these issues by a base level of pragmatism, but between those two groups on one side and radical/irrational anti-federal government ultra-conservatives on the other.
Interestingly, this problem is largely a perverse consequence of Republican efforts to maintain control of the House of Representatives through partisan gerrymandering, which has created dozens of congressional districts in which pragmatic governance is viewed as a fault in what the ignorami consider a zero-sum game for the heart and soul of "America."